Hydraulic transmission system

ABSTRACT

An hydraulic transmission system comprises a pump 10 with a housing 11, a rotor 12 therein and a plurality of radial pistons 13 in the rotor. A ring 14 surrounds the rotor and causes the pistons 13 to reciprocate in use. A servo device 25,26 for displacing the ring is fed by a pressure signal derived by a flow restrictor, through which liquid returning to the pump from an associated motor 21 passes. The speed of the motor is controlled automatically by variation of the eccentricity of the ring 14.

United States Patent Freeman Mar. 12, 1974 [54] HYDRAULIC TRANSMISSION SYSTEM 3,015,212 1/1962 Krafft et a1. 60/450 X [75] Inventor: Frank George Freeman, Solihull,

E l d ng an Primary Examiner-Edgar W. Geoghegan Assignee: Joseph Lucas (Industries) Limited, Attorney, Agent, or FirmHolman & Stern Birmingham, England Filed: July 10, 1972 Appl. No.: 270,283

Foreign Application Priority Data July 9, 1971 Great Britain 32260/71 US. Cl 60/450, 91/497, 417/213, 417/221 Int. Cl. F16h 39/46 Field of Search 60/450, 445, 449, 452; 417/212, 270, 213, 221; 91/491, 497

Kendrick 60/450 X [57] ABSTRACT An hydraulic transmission system comprises a pump 10 with a housing 11, a rotor 12 therein and a plurality of radial pistons 13 in the rotor. A 'ring 14 surrounds the rotor and causes the pistons 13 to reciprocate in use. A servo device 25,26 for displacing the ring is fed by a pressure signal derived by a flow restrictor, through which liquid returning to the pump from an associated motor 21 passes. The speed of the motor is controlled automatically by variation ofthe eccentricity of the ring 14.

5 Claims, 1 Drawing Figure HYDRAULIC TRANSMISSION SYSTEM This invention relates to hydraulic transmission systems and has as an object to provide such a system in a convenient form.

A hydraulic transmission system according to the invention comprises a pump having a housing, a rotor supported therein, a plurality of radial pistons slidable in the rotor, a ring surrounding the rotor engageable by the pistons and displacable to vary its eccentricity with respect to the rotor, a pair of ports in the rotor for fluid displaced by the pistons, passages communicating with the said ports and with a motor driven, in use, by the pump, a flow restrictor in one of the said passages, actuating means responsive to the difference in the fluid pressures on opposite sides of the restrictor to displace the said ring and means for biasing the ring towards one extremity of its displacement, the arrangement being such that an increase in the said fluid pressure difference urges the ring against the biasing means in a direction to reduce the strokes of the pistons.

Reference will now be made to the accompanying drawings which shows diagrammatically an example of a system according to the invention.

A pump has a housing 1 1 and a rotor 12 within the housing 11. Slidable in the rotor 12 are a plurality of pistons 13 whose outerends engage a ring 14 which is movable in a plane normal to the axis of the rotor 12 so as to have a varying degree of eccentricity with'respect thereto. Ports l5, 16 in the rotor 12 respectively communicate with passages 17, 18 in the housing 11.

Passages 17, 18 themselves communicate respectively with an inlet 19 and outlet 20 of a gear-type hydraulic motor 21. The passage 17 also connects with a chamber 29 defined between the housing 11 and rotor 12.

Passage 17 includes a flow restrictor 22, on respective sides of which are passages 23, 24 through which fluid pressure reaches actuating means in the form of pistons 25, 26 which are slidable in diametrically opposite radial bores in a part of the housing in side the ring which engage the ring 14 internally at diametrally opposed points. The piston is also acted upon by a spring 27 to bias the ring 14 to a position of maximum eccentricity with respect to the rotor 12. A fluid supply 28 communicates with the chamber 29 and hence with the port 16. A passage 30, including a non-return valve 31 effectively connects the passages 17, 18. The motor 21 is used to drive an external apparatus for example an alternator 32.

In use the pump 10 is driven by an external means, e.g., an internal combustion engine not shown, and operates in a known manner to produce a fluid flow which is dependent on the speed of the rotor 12 and the strokes of the pistons 13, the fluid in passages 17, 18

respectively being at high and low pressure. Fluid flow results in a proportionate pressure drop across the restrictor 22. The net force exerted on the pistons 25, 26 by the pressure difference in the passages 23, 24 causes the ring 14 to be displaced, against the bias of the spring 27, in a direction to reduce the strokes of the pistons 13. For a given fluid flow there will therefore be a corresponding eccentricity of the ring 14.

An increase in the speed of the rotor 12 results in an increased fluid flow which in turn acts as described to reduce the eccentricity of the ring 14 and hence to reduce the flow until an equilibrium condition is restored. A decrease in the speed of the rotor 12 similarly results in an increased eccentricity to restore an equilibrium condition. The rate of fluid flow from the pump 10, and hence the speed of the motor 21'may thus be maintained within predetermined limits, irrespective of the speed of the external driving means.

In an alternative arrangement the actuating means may be spherical and may conveniently comprise steel bearing balls.

I claim:

1. An hydraulic transmission system comprising a pump having a housing, a rotor supported therein, a plurality of radial pistons slidable in the rotor, a ring surrounding the rotor engageable by the pistons and displacable to vary its eccentricity with respect to the rotor, a pair of ports in the rotor for fluid displaced by the pistons, passages communicating with the said ports and with a motor driven, in use, by the pump, a flow restrictor in one of said passages, actuating means responsive to the difference in the fluid pressures on opposite sides of the restrictor to displace said ring and means for biassing the ring towards one extremity of its displacement, said actuating means comprising a pair of actuating elements slidable in diametrally opposite bores in the housing within said ring, said actuating elements engaging said ring internally and said bores communicating with said one passage on opposite sides of said flow restrictor, the arrangement being such that an increase in the said fluid pressure difference urges the ring against the biassing means in a direction to reduce the stroke of the pistons.

2. A system as claimed in claim 1 in which said actuating elements are pistons.

3. A system as claimed in claim 1 in which said actuating elements are balls.

4. A system as claimed in claim 1 in which said biasing means comprises a spring within one of said bores and acting on said actuating element.

5. A system as claimed in claim 1 in which the motor is a gear type motor. 

1. An hydraulic transmission system comprising a pump having a housing, a rotor supported therein, a plurality of radial pistons slidable in the rotor, a ring surrounding the rotor engageable by the pistons and displacable to vary its eccentricity with respect to the rotor, a pair of ports in the rotor for fluid displaced by the pistons, passages communicating with the said ports and with a motor driven, in use, by the pump, a flow restrictor in one of said passages, actuating means responsive to the difference in the fluid pressures on opposite sides of the restrictor to displace said ring and means for biassing the ring towards one extremity of its displacement, said actuating means comprising a pair of actuating elements slidable in diametrally opposite bores in the housing within said ring, said actuating elements engaging said ring internally and said bores communicating with said one passage on opposite sides of said flow restrictor, the arrangement being such that an increase in the said fluid pressure difference urges the ring against the biassing means in a direction to reduce the stroke of the pistons.
 2. A system as claimed in claim 1 in which said actuating elements are pistons.
 3. A system as claimed in claim 1 in which said actuating elements are balls.
 4. A system as claimed in claim 1 in which said biasing means comprises a spring within one of said bores and acting on said actuating element.
 5. A system as claimed in claim 1 in which the motor is a gear type motor. 